This invention relates generally to a process of abrasive-blasting and plasma etching a ductile-iron substrate to create surface oil reservoirs, which are then coated to provide a wear resistant iron article.
It has been recognized by researchers in the field of oil lubricated contacts, such as gears and rollers, that the lubrication of oil lubricated iron contacts is enhanced by physical vapor deposition (PVD) coatings. Wear-resistant PVD coatings applied to surfaces can enhance performance by reducing friction and wear. Typically, the deposition of a PVD coating on an iron substrate is accomplished by a chemical cleaning process, such as ultrasonic alkaline cleaning, followed by plasma etching, and then by the deposition process. Typically, iron articles that are relatively smooth or free from scale or oxides do not undergo an abrasive-blasting process prior to coating.
It has been theorized that in oil lubricated contacts, surface texture features, such as grooves or channels, for example, honed surfaces found in cylinder liners, can function as lubricant reservoirs. The reservoirs provide lubrication to the contact surfaces in situations which may be devoid of any lubrication, for example, during start-up or while in low speed motion. However, none of the prior art references teach or suggest a process to create surface oil reservoirs on an iron substrate for the purpose of improving lubrication.
It has long been desirable to have a process for improving the lubrication of iron parts. It has been even more desirable to accomplish the above objectives without detrimentally tempering the iron part.
None of the references teach or suggest surface oil reservoirs on the surface of the iron for the purpose of enhancing oil film thickness, friction coefficient, contact stresses and contact temperatures which influence pitting and scuffing performance.
In one aspect of the present invention, a process for increasing the lubrication of iron lubricated contacts is disclosed. The process comprises the following steps. An iron component having a ductile-iron substrate is provided. The surface of the ductile-iron substrate is abrasive-blasted and plasma etched to create surface oil reservoirs. A coating is then formed on the ductile-iron substrate by a deposition process.
In another aspect of the present invention, a ductile-iron article having improved lubrication characteristics is disclosed. The article comprises a ductile-iron substrate with surface oil reservoirs and a PVD coating deposited thereon.